Abstract
A recent taxonomic revision split the circumglobal sea hare Aplysia parvula into 10 constituent taxa, of which only three are likely to be found in the Southern Pacific. This prompted an investigation of animals previously identified as A. parvula from Australia. Specimens collected from Eastern Australia and Hunter Island, east of New Caledonia, could not be satisfactorily identified with any of the currently accepted taxa based on morphological diagnostic features listed in the revision; however, the presence of a highly concave shell is diagnostic. Quantification of genetic divergence using Cytochrome Oxidase I (COI) supports the delineation of this species as a distinct taxon, and a phylogenetic reconstruction based on concatenated COI, 16S and H3 markers reveals a sister relationship with the newly described Aplysia ghanimii from the Atlantic and Western Indian Oceans and an undescribed species from Japan. As a result, the name Aplysia concava G. B. Sowerby, I, 1833 is resurrected for this species. As the original description was based solely on a shell, a redescription is provided here with photographs of living animals and microscope images of internal anatomical structures.
Highlights
Many sea slug species previously thought to have wide, almost circumglobal distributions have been revised based on contemporary species delimitation methods using molecular data (e.g., Valdés et al [1]; Krug et al [2])
The name Aplysia parvula sensu stricto was retained for an Atlantic taxon, four names were resurrected for species from the Pacific and Indian Oceans, two species were described for the first time and two remain undescribed [3]
The aim of this study is to examine and redescribe Aplysia concava specimens using modern imaging techniques and to explore its phylogenetic relationship with other species among Aplysia parvula s. l. using data from partial Cytochrome Oxidase I (COI), 16S ribosomal DNA (16S) and Histone 3 (H3) gene sequences
Summary
Many sea slug species previously thought to have wide, almost circumglobal distributions have been revised based on contemporary species delimitation methods using molecular data (e.g., Valdés et al [1]; Krug et al [2]). The name Aplysia parvula sensu stricto was retained for an Atlantic taxon, four names were resurrected for species from the Pacific and Indian Oceans, two species were described for the first time and two remain undescribed [3]. Some of these taxa are short-range endemics, e.g., Aplysia elongata (Pease, 1860), which is only known from the Hawaiian Islands, or Aplysia japonica G. These comprised tissue from seven specimens sourced from the collection of the Australian Museum, Sydney (AMS), and four whole specimens collected from various locations in northern NSW by MN (Table 1; Figure 6)
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